Accretion definition, an increase by natural growth or by gradual external addition; growth in size or extent. See more.
Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream. Learn more about how they function and quiz your knowledge at the end.
Alveoli are small air sacs in the lungs, as small as a grain of sand.There are billions of these in the lungs, and the purpose of these alveoli are to supply de-oxygenated blood with a supply of oxygen through gas exchange.They are well-equipped to do this, as well.irst alveoli are coated with a substance known as surfactant to prevent them from collapsing. Second, there is a medium for immunoglobulins such â¦ as IgA to exist so that pathogens in the air can be defended against. Third, the air that enters the lungs is humidified to prevent drying and abrasion tissues.